1. Field of the Invention
The invention set forth in this specification is a method and apparatus for a power circuit breaker controller for use with high voltage switches.
2. Description of the Prior Art
It is well known to those familiar with switches used in high voltage lines that upon closure a voltage surge can be sent over the line and can be significantly increased in magnitude by the presence of trapped line charges. In some cases, the crest surge voltage can be more than double the value of the normal line bus voltage. If no protection were provided against these voltage line surges, too high a voltage would be placed on the adjacent and connecting equipment possibly causing damage to it. Several methods and types of equipment have been suggested and used to reduce these voltage surges. If the voltage surge causes a spark to jump a gap, massive amounts of insulation can be applied to prevent such from happening. However, when large areas are transversed by the high voltage power lines, like in the Pacific Northwest, the use of large amounts of line insulation has proven too costly. The emphasis has, as a result, been to try to concentrate on controlling the closing circuit breaker to prevent large voltage surges from happening. The two known publications which best describe the state of the art in this area are the U.S. Pat. No. 3,566,152 to Edward J. Casey et al and the C.I.G.R.E. Paper No. 143 by E. Maury published in 1966 by the Conference International de Grands Reseaux Electriquies in Paris, France. In the Casey patent, the first phase line to close occurs when the bus-side voltage loop is of the same polarity as the trapped line charge of the same phase line. The second and third phase lines are closed at staggered 30 to 120 electrical degree increments without consideration for bus-side voltage and trapped line charge polarities. This type of operation does not eliminate the possibility that surge voltages of about two times normal crest voltages can be present on the lines of the second and third phases upon closure. Further, when only one closing resistor is used with each phase line as in our invention, the Casey reference differs in that it does not use controlled synchronous closing of the main contacts to by-pass the closing resistors when the voltage across the closing resistor in each phase line is zero.
The E. Maury paper proposed that surge voltages be reduced by synchronizing closings of the main contacts of the breaker with voltage zero across the preinserted resistor. The exact initial instant the resistor is preinserted did not appear important. This is contrary to our findings that it is absolutely necessary for the preinserted resistor contacts be closed when the polarity of the bus-side voltage and the trapped charge is the same.